Admission procedures and security checks for events at the West Kowloon arts hub will be reviewed to ensure organisers learn the right lessons after one fan died and three others were admitted to hospital during an electronic music festival on Saturday, the cultural district chief has pledged.

CEO of the West Kowloon Cultural District Authority Duncan Pescod promised an investigation on Tuesday as the Post learned the three victims admitted to hospital had tested positive for controlled drugs, which could either be party or prescribed pills.

The four victims – all Hongkongers – fell sick at different times, from 3.35pm to 11.41pm, during the festival called Road to Ultra held on the grass pitch in the Nursery Park area of the district on Saturday. Investigations showed they had not carried illegal drugs, according to police.

One of the four, Chow Wai-ho, 27, died on Saturday night and the others – a woman, 21, and two men, 22 and 29 – remained in critical condition at Queen Elizabeth Hospital in Yau Ma Tei. The woman is understood to have an underlying heart problem.

Two small plastic bags containing ecstasy and tranquilliser Midazolam were found by police on the event site on Sunday morning.

Ahead of the authority’s board meeting on Monday afternoon, Pescod, said security measures adopted by event organisers were considered when deciding whether to rent a venue to applicants.

He promised that the authority would review details of the admission process, including security checks and personnel arrangements for events to be held at the arts hub “to make sure we learn the appropriate lesson”.

Pescod said 100 security officials were present at the event and that festival goers underwent security checks. There were three first aid stations at the park.

But he maintained the admission procedures also had to be “practical”.

“You had nearly 10,000 people on the site. You have to have a system to ensure that people could get in quickly and efficiently but at the same time, proper bag search is carried out, which was exactly what was put in place,” he said.

He added it was important to make sure every external hirer knew their expectations, such as having zero tolerance for illegal activities.

Road to Ultra, which first landed in Hong Kong last year, was one of the external hirers’ events. Pescod said the authority also intended to review its procedures to make sure all the terms and conditions for events would be properly observed.

A government source with knowledge of the case said further tests were to be conducted on the three victims admitted to hospital to determine the kind of drugs they had taken while an autopsy would be carried out on Tuesday to learn whether drug use was related to Chow’s death.

“We will also look into their medical backgrounds as part of our investigation,” he said.

Police were still poring over security camera footage to ascertain whether dealers sold illegal drugs at the venue.

Describing the task as “finding a needle in a haystack”, a police source said: “The venue is huge and thousands of people took part in the event.”

Detectives from the Yau Tsim district crime squad are handling the case.

The source said police were also investigating whether hot weather and alcohol consumption were among factors that led to the victims’ collapsing while at the park.

A spokesman for the West Kowloon Cultural District Authority said on Sunday it understood the four had been sent to hospital because they suffered from heatstroke.